Embodiments of the present disclosure generally relate to implantable medical devices, and more particularly to implantable medical devices that communicate with an external device through radio frequency (RF) signals.
Numerous medical devices exist today, including but not limited to electrocardiographs (“ECGs”), electroencephalographs (“EEGs”), squid magnetometers, implantable pacemakers, implantable cardioverter-defibrillators (“ICDs”), neurostimulators, electrophysiology (“EP”) mapping and radio frequency (“RF”) ablation systems, and the like. Implantable medical devices (hereafter generally “implantable medical devices” or “IMDs”) are configured to be implanted within patient anatomy and commonly employ one or more leads with electrodes that either receive or deliver voltage, current or other electromagnetic pulses (generally “energy”) from or to an organ or tissue for diagnostic or therapeutic purposes.
Various IMDs are monitored by a programmer or base station that is remotely located from the IMDs. For example, a patient may have an IMD that communicates with a base station within the patient's home. The base station may be located by a patient's bedside. The base station receives data from the IMD regarding the patient's physiological state and/or the operation state of the IMD. Based on the received data, the base station may convey the data to a remote server of a medical care network, or adjust operating parameters for the IMD. For example, the base station may adjust operating parameters of the IMD, such as when a patient experiences changes in arrhythmia, pacing, ST shift, various types of ischemia, base rate, and the like.
Many IMDs include an RF capability to communicate with the programmer. Data may be received from the base station when transmitted over varies frequency bands, such as at a 402-405 MHz frequency range, which represents the Medical Implant Communication Service (MICS) band. The MICS band enables a short-range, wireless link to be maintained between low-power implanted IMDs and an external programmer or base station.
An RF chip within a typical IMD periodically scans select frequency bands, such as the 2.45 GHz band, over the life of the IMD. The 2.45 GHz band is an unlicensed, microwave band. The IMD uses information received over the 2.45 GHz band to determine if the programmer is seeking to communicate with the IMD over another band (for example, the MICS band), which is used to receive and transmit data to and from the IMD. If the RF chip operating at a 2.45 GHz band detects that the programmer desires to communicate over the MICS band, the IMD then switches over to the MICS band. Bidirectional communication over the MICS band consumes substantially more power than the 2.45 GHz band. As such, through the use of the 2.45 GHz band, which is used to detect whether the programmer is attempting to communicate with the IMD, the IMD conserves energy. In general, the MICS band (for example, the 402-405 MHz band) affords a longer range and more robust connection than the 2.45 GHz band. However, as compared to the MICS band, the 2.45 GHz band draws less power from the IMD when scanning for connection requests and during a communications session.
The MICS band has been used with IMDs such as pacemakers. In general, communication between a pacemaker and a base station may occur less than five times per day, with each communication session being relatively short, such as less than two or three seconds.
In contrast, certain IMDs, such as neurostimulators-communicate with a base station with increased frequency, as compared to pacemakers, and for longer periods. Accordingly, neurostimulators typically communicate with base stations through inductive communication, as communication using the MICS band typically draws excessive power from the neurostimulators. In an inductive communication system, communication may occur between the IMD, such as a neurostimulator, and a telemetry wand that is operatively connected to the base station. Typically, the wand of the base station or programmer is placed in close proximity to the IMD in order to establish a communication link.
Accordingly, use of the MICS band to facilitate communication between a neurostimulator and a base station has generally not been considered because the neurostimulator would need to use an amount of energy to communicate using the MICS band that would reduce the longevity of the neurostimulator.